Eating Fish Can Decrease Risk for Heart Disease

< July 30, 2008 > -- Near-daily consumption of fish over a lifetime is thought to be the reason that Japanese men are far less likely to have dangerous plaque build-up in their blood vessels than caucasian or Japanese-American men. This difference is seen even in light of high levels of smoking in the Japanese male population.

"Japanese living in Japan eat fish every day, about 100 grams [3.5 ounces] every day," says study author Dr. Akira Sekikawa. "They also have very low rates of coronary heart disease, even with a high rate of smoking and other risk factors."

Dr. Sekikawa is an assistant professor of epidemiology at the Graduate School of Public Health at the University of Pittsburgh in Pennsylvania. Results of the study are published in the Journal of the American College of Cardiology.

Heart and Neck Arteries Affected

Dr. Sekikawa's study included 281 Japanese men, 306 caucasian American men, and 281 Japanese-American men. Along with giving blood samples, all of the men underwent electron beam computed tomography (EBCT) to measure coronary artery calcification (plaque deposits in the heart's arteries) and ultrasound examinations of the carotid artery in the neck.

Overall, the researchers found that Japanese-American men had the highest number of heart disease risk factors of all three groups. They had the highest average body-mass index (BMI), blood pressure, triglycerides, and the highest levels of diabetes.

The Japanese men living in Japan had far higher rates of smoking - 47 percent - and smoking is one of the most significant heart disease risk factors.

But they had significantly less coronary artery calcifications and less build-up in their carotid arteries.

The levels of omega-3 fatty acids in the blood were 9.2 percent for men living in Japan, 3.9 percent for caucasian men, and 4.8 percent for Japanese-American men. Yet, Japanese-American men had more coronary artery calcifications and more build-up in their carotid arteries than the caucasian men and the men in Japan.

Fish Consumption Important

"Fish is an important factor in keeping the Japanese healthy," says the author of an accompanying editorial, William Harris, Ph.D., director of the Metabolism and Nutrition Research Center, Sanford Research/USD, in Sioux Falls, SD.

"The combination of increased fish oil and a low saturated fat diet is probably the best way to lower heart disease risk. Eskimos have a diet high in omega-3s, but also high in saturated fat, and they don't have the same low levels of heart disease," he adds.

Dietary Recommendations

Current American Heart Association (AHA) guidelines recommend eating oily fish, such as salmon or albacore tuna, at least twice a week if you do not have heart disease. If you already have heart disease, the AHA suggests getting at least one gram of omega-3 fatty acids daily, preferably from fatty fish. However, the AHA cautions that you should not consume more than two grams of fish oil daily without first consulting your doctor, because of a risk of excessive bleeding.

Dr. Harris says it is important to consume fish or fish oil on an ongoing basis. "A month of supplements won't get you there," he says. But, if you do not like fish, he says that fish oil supplements can also improve your health. However, he suggests that you read the supplement label and make sure that each capsule contains one gram of omega-3s. And, he says, they do not have to be expensive to be effective.

If you do not have heart disease, he says, two grams a day "is more than adequate." And, if you like fish, that is even better.

"Choose oily fish, not fried fish, but fish that naturally contain omega-3s, like salmon, sardines, albacore tuna, herring, and mackerel, and you need to eat about two 4-ounce servings a week," Dr. Harris adds.

Always consult your physician for more information.

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More About Fish and Omega-3s

The American Heart Association (AHA) says that omega-3 fatty acids benefit the hearts of healthy people, and those at high risk of - or who have - cardiovascular disease.

In 2002, the AHA released a scientific statement, “Fish Consumption, Fish Oil, Omega-3 Fatty Acids and Cardiovascular Disease,” on the effects of omega-3 fatty acids on heart function (including antiarrhythmic effects), hemodynamics (cardiac mechanics), and arterial endothelial function. The link between omega-3 fatty acids and cardiovascular disease risk reduction are still being studied, but research has shown that omega-3 fatty acids provide these benefits:

decrease risk of arrhythmias, which can lead to sudden cardiac death

decrease triglyceride levels

decrease growth rate of atherosclerotic plaque

lower blood pressure (slightly)

The AHA recommends eating fish (particularly fatty fish) at least two times a week. Fish is a good source of protein and does not have the high saturated fat that fatty meat products do.

The AHA also recommends eating tofu and other forms of soybeans, canola, walnuts and flaxseed, and their oils. These contain alpha-linolenic acid (LNA), which can become omega-3 fatty acid in the body. The extent of this modification is modest and controversial, however. More studies are needed to show a cause-and-effect relationship between alpha-linolenic acid and heart disease.

This guide to use for consuming omega-3 fatty acids is offered by the AHA:

Patients without documented coronary heart disease (CHD) should eat a variety of (preferably fatty) fish at least twice a week. Include oils and foods rich in alpha-linolenic acid (flaxseed, canola, and soybean oils; flaxseed and walnuts).

Patients with documented CHD should consume about 1 gram of EPA+DHA per day, preferably from fatty fish. EPA+DHA in capsule form could be considered in consultation with the physician.

Patients who need to lower triglycerides should take 2 to 4 grams of EPA+DHA per day provided as capsules under a physician’s care.

Patients taking more than 3 grams of omega-3 fatty acids from capsules should do so only under a physician’s care. High intakes could cause excessive bleeding in some people.

A word of caution from the AHA: Some types of fish may contain high levels of mercury, PCBs (polychlorinated biphenyls), dioxins, and other environmental contaminants. Levels of these substances are generally highest in older, larger, predatory fish and marine mammals.

Always consult your physician for more information.

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